Bulked non-wovens



Aug. 13, 1963 w. T. ALLMAN, JR., ETAL 3,100,328

BULKED NON-WOVENS Filed Dec. 4, 1958 United States Patent 3,1lli3,328 BULK-ED NON-WOVENS William T. Allman, In, (Iharles W. .ioseph, and Ralph G.

Higgins, In, Rock Hill, SAL, assignors to Celanese Corporation of America, New York, N.Y., a corporation of Delaware Filed Dec. 4, 1958, Ser- No. 778,248 10 Claims. (Cl. 28'76) The present invention relates to novel non-woven articles characterized by high bulk and a soft hand.

It is an object of the invention to provide non-woven filamentary materials of increased covering power, resilience, insulation and strength as well as of softer hand.

Other objects and advantages of the invention will become apparent from the following detailed description and claims.

In accordance with one aspect of the present invention, a non-woven article comprising organic acid ester of cellulose filaments bonded to one another at spaced locations is subjected to steaming whereby the physical properties of the article are changed, viz. the covering power is increased along with the resilience, insulation and strength while the density is decreased and the hand is improved.

The steaming is advantageously carried out at a temperature ranging from about 95 to 180 C. and preferably 110 to 125 C. The pressure is generally superatmospheric but atmospheric or even reduced pressure may prevail.

The duration of the steam treatment will depend upon the temperature and upon the thickness and construction of the article being treated. Generally it will be at least about 1 minute to produce a substantial improvement and it may be as long as 10 minutes or more. At the preferred temperatures the duration of steaming is preferably about 1 to 5 minutes.

The non-woven article may comprise a web, fleece or sheet material composed of staple length fibers either randomly disposed or oriented to a greater or lesser degree as by carding, the fibers being bonded to one another at spaced points.

In accordance with another aspect of the invention, the non-woven article comprises a web, fleece or sheet material composed of substantially randomly directed substantially continuous filaments bonded to one another at spaced points of contact. Advantageously such webs may be formed as described in detail in copending application Serial No. 744,844, filed June 26, 1958. Briefly, filament-forming material in liquid phase is extruded through a plurality of orifices to form continuous filaments which may be agitated, such as by biasing with air, while still mutually adhesive, to cause them to swirl about and coalesce randomly. The filaments are continuously drawn away from the extrusion location in the form of a nonwoven web or fleece. The web so produced can be directly steamed or it may be subjected to intermediate treatments such as hot calendering to increase the number of points of fusion and the density. Various adsorbents, pigments, etc. can be incorporated in the non-woven either by being added to the dope which is being spun or by being deposited on the web as formed.

The denier of the individual filaments of the non-woven may vary within wide limits, e.g. from less than 1 up to 20 or more, although preferably it ranges from about 2 to 16. The weight per square yard of the non-woven can also vary widely, depending upon its thickness, density, etc.

The filamentary material may comprise an organic acid ester of cellulose such as cellulose acetate, cellulose propionate, cellulose butyrate, cellulose acetate propionate, cellulose acetate butyrate, or the like. The esters may be triesters, i.e. esters containing fewer than about 0.29 free filaments of a cellulose triester and of a secondary cellu-v lose ester, e.g. cellulose triacetate and conventional cellulose acetate. This can be formed by simultaneously extruding a solution of cellulose triacetate in methylene chloride through one set of orifices and extruding a solution of conventional cellulose acetate through a second set of orifices. The filaments formed by such extrusions are positioned near each other and a blast of air causes them all. to swirl and entangle with one another, becoming fused at spaced points. Steaming produces exceptionally high bulk because of the effect on the filaments individnally as well as because of the differences in the thermal characteristics of the different types of filaments.

While not wishing to be bound thereby, the change in physical properties upon steaming is believed due to the following effects: Upon drying of freshly formed cellulose ester filaments, especially of substantially continuous filament non-Wovens wherein the filaments are fused at spaced points of contact, the filaments undergo compression or other stresses between fusion or weld points. During the subsequent steaming the stresses are released and the filaments become distorted into sinusoidal, helical or other three-dimensional crimp-like configurations between the welds. In addition, the filaments are somewhat softened and make additional bonds with adjacent filaments as the expansion creates new points of contact. The

movement of the filaments increases the interlocking of filaments so that the final structure is stronger, in addition to being less dense as a result of the three-dimensional bulking. At the same time there is an improvement in the hand of the non-woven, i.e. it becomes softer.

In the event that the filamentary material of the nonwoven is initially more or less oriented and the non woven accordingly much stronger in one direction than another, the steaming decreases the orientation and reduces the differential strength.

In spite of their increased strength and abrasion resistance, the products may be completely free of extraneous binders and/ or plasticizers.

The steaming treatment can be eflected with the nonwoven starting material in sheet form either flat or wound in a roll loosely about a shaft. Alternatively the nonwoven may be in a form approximating that required for an end use, e.g. it may be wound about a perforated cylindrical core in a form suitable for use as a cylindrical oil filter cartridge. The non-woven may be incorporated as an interlining or filling material between layers of fabric or the like and the composite article may be subjected to steaming. In general, the product will be useful wherever non-Wovens have heretofore found application.

The invention will be more fully described with reference to the accompanying drawing, wherein:

FIG. 1 is an elevation of an apparatus for forming a composite non-woven, with the front cover shown in section;

FIG. 2 is an elevation of a steaming apparatus with the front cover shown in section;

FIG. 3 is a plan View of a non-woven sheet prior to steaming; and

FIG. 4 is a plan view of the sheet of FIG. 3 after steaming.

Referring now more particularly to the drawing, in FIG. '1 there is shown a closed cabinet 11 housing an endless highly porous member such as a wire screen 12 trained about shafts 13, 14, at least one of which is rotated, at relatively low speed, so that the top of screen 12 moves to the right. Hot air is admitted to the cabinet 11' through a line 15 and leaves with solvent vapors through an exhaust 16.

A first solution of filament forming'material, e.g. conventional cellulose acetate in acetone, is extruded as a which leaves cabinet 11 through an opening defined by a I pair of rolls, 22, 23 which prevent excess leakage of solvent vapors from the cabinet. The fleece 21 is taken up loosely on a roll 24 simultaneously with a separating web 25 such as paper unrolled from a supply package 26. When the roll 24 reaches a predetermined size the fleece 21 and web 25 supplying the roll 24 are cut, the roll 24' is removed and a new roll is started.

The roll 24 of predetermined size is placed in an enclosure 26 (FIG. 2) and steam is admitted through line 27 with all other lines closed. After a predetermined time line 27 is closed to terminate steaming, line 28 is opened and relatively-cool air is forced in through line 29 to purge the steam and to cool the roll 24. The roll 24 is then removed and can be used in conventional manner, stripping the paper separator 25 as the roll is unwound.

In FIG. 3 there is shown a non-woven sheet material 30 composed of substantially continuous filaments 3 f relatively high denier. The sheet is very fiat and has a high gloss and stiff hand, the filaments having a plastic rather than a textile appearance. After steaming, the product has the appearance illustrated in FIG. 4. The sheet is about twice as thick, the luster is reduced considerably and, while still somewhat stifi", the feel is similar to that of a starched natural fiber web rather than a plastic. In addition, the individual filaments are characterized by numerous crimps extending in three dimensteam.

sions which increase the covering power of the article.

The following examples are given to illustrate the invention further. 7

7 Example I Using the apparatus shown in FIG. 1, except that spinnerette 18 is inoperative, a heated dope of cellulose acetate in acetone is extruded through spinnerette 17 provided with 60 circular orifices each 126 microns in diameter. The linear speed of extrusion through the orifices is 3750 meters per minute, and the speed of screen 12 is 75 meters per minute. The denier of the*filamcnt8 of the non-woven ranges from about 2 to 7 and its weight is 2 ounces per square yard. This material is illustrated in FIG. 3 of the drawing. After autoclaving for 8 minutes with steam at 121 C. and 15 p.s.i.g. the non-woven shrinks in width from an initial value of 4.5 inches down to 4.3 inches. The sheet weighs about 2.1 ounces per square yard and its thickness has increased fromabout 0.02 to 0.06 inch. The product is illustrated in FIG. 4.

It is to be understood that the foregoing detailed description is given merely by way of illustration and that many variations may be made therein without departing from the spirit of our invention.

2. The process which comprises moving filaments of a lower alkanoic acid ester of cellulose While they are in adhesive condition to cause them to become randomly directed and bonded to one another at spaced points so as to form a non-Woven sheet-like article, and contacting said article with steam at a temperature ranging from about to 180 C.

.7 3. The process set forth in; claim 2 wherein the duration of said contact with steam is at least about one minute.

4. The process set forth in claim 2 wherein said nonwoven article comprises substantially continuous substantially randomly directed lower alkanoic acid ester of cellulose filaments.

5. The process which comprises moving filaments of a lower alkanoic'acid ester of cellulose to cause them to become randomly directed and to touch at spaced points and bonding said filaments at said points so as to form a non-woven sheet-like article, and contacting said article with steam at a temperature ranging from about to C.

6. The process which comprises moving substantially continuous cellulose acetate filaments while they are in adhesive condition to cause them to become substantially randomly directed and bonded to one another at spaced points so as to form a non-woven sheet-like article, and contacting said article with steam at a temperature ranging from about 95 to C. for at least about one minute.

7. The process set forth in claim 6 wherein said filaments comprise secondary cellulose acetate filaments. .8. The process set forth in claim 6 wherein said filament-s comprise a mixture of secondary cellulose acetate filaments and cellulose triacetate filaments.

9. The process which comprises moving substantially continuous filaments of a secondary cellulose ester of a lower alkanoic acid and substantially continuous filaments of a cellulose triester of a lower alkanoic acid while said filaments are in adhesive condition to cause them to become randomly directly and bonded to one another 'at spaced points so as to form a non-woven Web containing intermixed filaments, and steaming said Web.

' 10. The process which comprises contacting with steam a non-woven sheet-like article of randomly directed filaments of organic acid ester of cellulose bonded at spaced points, said. contacting with steam being such that three dimensionahcrimplike configurations are formed in said filaments between said bonds and said article increases in thickness.

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6. THE PROCESS WHICH COMPRISES MOVING SUBSTANTIALLY CONTINUOUS CELLULOSE ACETATE FILAMENTS WHILE THEY ARE IN ADHESIVE CONDITION TO CAUSE THEM TO BECOME SUBSTANTIALLY RANDOMLY DIRECTED AND BONDED TO ONE ANOTHER AT SPACED 